ADDIS ABABA, ETHIOPIA
— On the surface, the reasons for rising tensions between the African nation of Ethiopia and its tiny neighbor, Eritrea, may seem trivial. The two are on the verge of restarting the bloodiest interstate war in Africa in recent memory, ostensibly over a border town called Badme - a desert outpost with just 5,000 people.

But dig deeper into the precarious internal situation both regimes face, as well as the region's interlaced alliances, and it's clear the dangers of a reignited war are great for the region.

Ethiopia, for instance, is an anchor of strength and relative stability in its broader region, which includes volatile Somalia and Sudan. How it reacts toward Eritrea - with aggression or restraint - may determine the region's progress in coming years.

In all, how Ethiopia-Eritrea tensions are resolved "is going to define Ethiopia's role in the region" - and, to a large extent, the region's future, says Matt Bryden of the International Crisis Group in Pretoria, South Africa.

The growing focus by the United Nations and others on preventing war highlights the importance of the conflict. UN peacekeeping chief Jean-Marie Guéhenno, for instance, visited Eritrea recently to try to defuse tensions. But top officials refused to meet him.

Both countries failed to comply with a Nov. 23 Security Council resolution that gave 30 days for: Ethiopia to begin work to demarcate its border in compliance with a 2002 decision by a UN-sponsored Boundary Commission; Eritrea to lift restrictions on the UN Mission in Ethiopia and Eritrea (UNMEE); and both countries to pull back troops on the border to their December 2004 levels. Failure to meet these requirements means both countries could face UN sanctions when the Security Council deliberates on the issue next month.

The UN recently pulled US, Canadian, and European peacekeepers out of the border zone - after Eritrea ordered them to leave. Eritrea's move was widely seen as exasperation with the UN's failure to enforce the 2002 ruling that awarded Badme to Eritrea. Ethiopia has refused to abide by the ruling.

Eritrea's not-so-subtle threat is that if it doesn't get Badme it will restart the 1998-2000 war - a World War I-style conflict in which both sides hunkered down in trenches and sent waves of soldiers into enemy fire. Some 70,000 were killed.

In unpacking the reasons for the tension, several things are crucial.

One is that internal political dynamics threaten both governments. "This is about regime survival for both of them," says Alex de Waal, an Africa expert at Harvard University.

Indeed, the question of Badme is tricky for Ethiopia's Prime Minister Meles Zenawi. His troops conquered the town in the recent war. Then the Boundary Commission told him to give it back. His hard-line critics see it as a point of national pride that Ethiopia should keep Badme. "If you had just fought and won on the ground - and then were told to surrender those gains," it's problematic, explains Mr. Bryden. "People might try to assassinate him" if he concedes, adds Admore Kambudzi, an official at the African Union, a kind of UN of Africa based in Ethiopia's capital.

One hint of Mr. Meles's insecurity is his harsh response to criticism. With election-related violence plaguing the country for several months, 131 opposition figures were charged this month with treason.

Eritrea's regime, meanwhile, is one of Africa's most repressive. In a country of just 4.5 million, it has imprisoned 15 journalists - more than any other country except China and Cuba - according to a report by the Committee to Protect Journalists.

President Isaias Afwerki's government also has many internal enemies, including dozens of political dissidents who have been imprisoned. "The only way for him to stay in power is to say, 'Ethiopia is coming to get us,' " says de Waal.

Also a key reason war between the two could cause wider trouble is because Ethiopia is a major power in a tough neighborhood.

"What the region is looking for - and needs - is a power that guarantees stability through predictable behavior," says Bryden. This stability is what Ethiopia has sought to provide, and is the reason donor countries have been reluctant to press the government too hard.

But if Ethiopia continues to reject the 2002 Boundary Commission ruling, Bryden says, it will cement its reputation as acting by "might rather than right," which will "make all the neighbors worried."

Eritrea also has the capacity to stir up trouble in the region, experts warn. It financed arms for Somali Islamic extremists in the mid-1990s, de Waal says. And it has ties to Darfur rebels in Sudan, which it could encourage to stoke the war there.

Next door to Darfur, trouble brewing in Chad

Keep an eye on Chad, warn Africa experts. With its ailing and paranoid president, its expanding oil exports, and its proximity to Sudan, the desert nation is at great risk of becoming a major African flashpoint.

In the past week, Chad has accused neighboring Sudan of backing rebel groups that have launched recent attacks in eastern Chad and of trying to draw it into the fighting in Sudan's Darfur region.

Chad's ill and isolated president, Idriss Deby, is so paranoid that "he doesn't even trust his own family," says Alex de Waal, a Harvard University expert on Africa. And for good reason: Two of his cousins - top officials in the all-important oil and cotton industries - recently defected from his government. At issue is who will take over when Mr. Deby dies. Rebels, reportedly led by Army deserters who are calling for Deby to step down, are massing in the country's east.

Home to some 10 million people, Chad is one of the world's poorest nations, but also one of Africa's newest oil producers. Yet it recently pulled out of a program designed by the World Bank that aimed to ensure its oil riches would reach its people - not just enrich the elites. Now military budgets are growing.

Also, the ethnic and military ties between Chad and Darfur could mean fighting in Chad will exacerbate the ongoing conflict in Darfur.